This invention relates to the field of undercutters. Undercutters are used to scoop out contaminated gravel from beneath railroad tracks. These devices employ a chain mechanism pulled by drive means around an elongated bar in a manner similar to that of a chain saw. An undercutter however utilizes a much larger chain and cutting mechanism, and exists in an extremely abrasive environment. Thus, by its nature the chain is extremely heavy, several hundred pounds, requiring two or more men to lift and remove it to gain access to the bar for replacement or adjustment, and difficult to do in the field without lifting equipment.
Adjustment of the chain is necessary after periods of use due to stretching of the chain, or other reasons that cause the chain to loosen. Consequently, work must be stopped, hand tools are then used to access the adjusting screws near the tip of the bar to extend the bar so as to tighten the chain against it. This is time consuming and results in lost labor hours, and lost productivity of the undercutter when not in use. It is estimated that at least twenty minutes is lost every two hours or so as a result of stopping and adjusting. Furthermore, operators must keep chain tension in mind in addition to the many other operational and safety issues of which they must be aware. The chain can go slack by taking too big of a bite, causing extra stops to adjust. Thus one object of the invention is to provide an automatic chain adjusting mechanism, that not only will avoid the otherwise lost labor involved, but will also provide the adjusting while in use, and without work stoppage so as to avoid downtime of the undercutter.
Consistent tension is also a problem. When hand tightening, the resulting chain tension is often inconsistent and not at the optimum tension. The chain wears best, and lasts longest, with the proper tension, and hand tightening doesn't always allow for the correct tension. Moreover, and just as significant, during use the chain tension itself loosens gradually. Thus the chain is seen to have a substantial amount of use under less than optimum chain tension. Until the chain is tightened back to the optimum tension, continued use of the undercutter creates unnecessary wear and tear on the slack chain. Moreover, loose chains are more likely to have debris caught in them, or to break, creating safety hazards. Thus an object of the invention is to also provide for a chain adjusting mechanism that adjusts essentially continuously so as to provide a constant desired chain tension during use
A safety hazard, as well as unnecessary wear and tear, can occur when the chain suffers sudden shocks and stresses during use. In the harsh environment in which an undercutter is used, such hazards are not uncommon. A shock absorbing mechanism is needed to avoid stresses from such shocks, thus it is a further object to provide such a shock absorbing mechanism.
It is a further object of the invention to provide a self adjusting chain mechanism that utilizes existing hydraulic means used in connection with the undercutter itself, and even to work in conjunction with the hydraulics of the excavator to which the undercutter is attached.
No known devices provide these features in the heavy duty undercutter environment.
Other features and objects will be apparent from the disclosure herein.